Abstract: Surface low is one kind of the surface defects in automobile exterior stamping panels. It has a great influence on the cosmetic appearance of automobile. A door handle part according to the character of the automobile door exterior panel is designed. In order to determine the distribution of surface deflections, the part is grinded with oil stone and measure the contour curves by a stylus instrument, respectively. Finite element simulations of representative surface deflection parts are conducted to observe the local deformation and the distribution of residual stress in surface deflection areas. The mechanism of various surface deflections is explained, respectively. The research indicates that insufficient bending and stretching, the effect of bending and unbending effect and the local buckling under compressive stress are the mechanism of surface deflections. The work reveals the diversity of the mechanism of surface deflections and provides the theoretical evidence for quality control of surface deflections in automobile exterior panels.

Key words: Automobile exterior panel, Numerical simulation, Springback, Stamping, Surface low